Project’s based on Sarah Mlynowski’s book about an angst-ridden teenage girl who discovers that her socially inept younger sister — and not she — has inherited her divorced mother’s magical powers. Despite the mother’s warning not to cast spells, the younger sister succumbs to temptation, with disastrous results.

Roberts, the 13-year-old niece of Julia Roberts, is co-starring with Sara Paxton in Fox 2000’s mermaid fantasy “Aquamarine,” which Cartsonis is producing. Elizabeth Allen is the director on “Aquamarine,” now shooting in Australia.

Cartsonis also is a producer on Paramount’s “Daughter of the Queen of Sheba.” Lasse Halstrom is attached to direct.